(1) Technical Field
The present invention relates to field of optical and radio communications. More specifically, the present invention relates to a mechanism for generating modulated waveforms by combining a plurality of harmonics belonging to an impulse signal.
(2) Discussion
Radio transmissions are currently used to send signals, i.e. waveforms, over the air for receipt by receivers. One of the chief difficulties suffered by radio systems is providing a faithful reproduction of the transmitted signal. Current radios suffer from inadequate ability to reproduce incoming waveforms, particularly complex waveforms, and from limited bandwidths.
It is therefore desirable to provide a radio signal generation and transmission mechanism that can faithfully reproduce a modulated waveform and that is capable of utilizing a wide bandwidth.
The present invention provides an opto-electronic modulation apparatus for a UWB radio system. The opto-electronic modulation apparatus comprises an optical modulator block for receiving a UWB harmonic impulse signal and for modulating the UWB harmonic impulse signal based on data received through an input to the modulator block in order to generate a modulated UWB signal for launching by a UWB transmitting block.
In another aspect, the modulation apparatus is configured to receive a UWB harmonic impulse signal in a form of a pulse stream of components, and to modulate each of the pulse stream components, except a beating component, based on data received through the input to the modulator block.
In still another aspect, the means for opto-electronically modulating a signal is a digital optical modulator.
In yet another aspect, the modulator block comprises an electro-optical intensity modulator.
In addition, the modulator block may be selected from a group consisting of electro-absorption modulators and LiNbO3 modulators and provides for on/off keying.
In a further embodiment, the modulation block has a modulation rate, and wherein the modulation rate is variable.
In a still further embodiment, the opto-electronic modulation apparatus further comprises a means for adjusting a pulse repetition frequency of an optical comb generator that supplies the pulse stream to the opto-electronic modulation apparatus.
Further, the modulation rate is variable by means of harmonic selection.
In a further embodiment, the opto-electronic modulation apparatus further comprises a voltage-controlled oscillator connected with the modulator block and with an optical comb generator that supplies the pulse stream to the modulation apparatus to allow for a continuous modulation rate change around a comb fundamental frequency.
In yet another embodiment, the pulse stream modulation block comprises an electro-optical phase modulator configured to impose a polarity modulation scheme onto the UWB harmonic impulse signal based on the data input. In this case, the electro-optical phase modulator can be configured to modulate the pulse stream components using a 180 degree phase shift to provide a bipolar phase shift-keying modulation scheme.
The modulation apparatus can also be configured to receive a single reference tone from a UWB harmonic impulse signal comprised of component tones, and to modulate a single reference tone of the component tones based on data received through the input to the modulator block to generate a beating note for beating with other component tones of the UWB harmonic impulse signal for generating difference notes for launching by a UWB transmitting block.
In another aspect, the means for opto-electronically modulating a signal is a digital optical modulator.
The modulator block can also be configured as an electro-optical intensity modulator that modulates the single reference tone by on/off keying.
In another aspect, the means for opto-electronically modulating a signal is an analog optical modulator.
In still another aspect, the optical modulator block comprises an acousto-optic modulator for receiving analog data and for providing an output signal based on the received analog data; a tapered waveguide Fiber Bragg Grating (FBG) having a reflective length, the waveguide FBG connected with the acousto-optic modulator and responsive to the output of the acousto-optic modulator such that the reflective length of the tapered waveguide array varies in response to signals from the acousto-optic modulator; and a circulator connected to receive the single reference tone and to pass the single reference tone to the tapered wave guide array to be modulated thereby according to changes in the reflective length, and then to a UWB transmitting block as a beating note; whereby an analog pulse-position modulation scheme is used to generate a modulated UWB signal for launching by a UWB transmitting block.
The modulator apparatus may further comprise an FM modulator for receiving and FM-modulating analog data, and for providing the modulated analog data to the modulator block through the input; whereby the FM modulator is used to drive the modulator block to cause the modulator block to impose FM-modulated data onto the single reference tone.
Further, the means for opto-electronically modulating a signal comprises a means for receiving a UWB harmonic impulse signal and for modulating the UWB harmonic impulse signal based on data in order to generate a modulated UWB signal for launching by a UWB transmitting block.
In a further aspect, the means for opto-electronically modulating a signal is configured to receive a UWB harmonic impulse signal in a form of a pulse stream of components, and to modulate each of the pulse stream components, except a beating component, based on data received through the input to the modulator block.
In yet another aspect, the means for opto-electronically modulating a signal further comprises a means for adjusting a pulse repetition frequency of an optical comb generator that supplies the pulse stream to the means for opto-electronically modulating a signal.